The origin of the word cuttlefish can be found in the old English term cudele, itself derived in the 1400s from the Norwegian koddi (cushion, testicle) and the Middle German kudel (pouch), a literal description of the cephalopod's shape. The Greco-Roman world valued the cephalopod as a source of the unique brown pigment released from its siphon when alarmed. Hence, the word for it in Greek and Latin is sepia (later seppia in Italian).

Anatomy

Cuttlebone

Cuttlefish possess an internal structure called the cuttlebone, which is porous and composed of aragonite, to provide the cuttlefish with buoyancy. Buoyancy can be regulated by changing the gas-to-liquid ratio in the chambered cuttlebone via the ventral siphuncle.[3] Each species has a distinct shape, size, and pattern of ridges or texture on the cuttlebone. The cuttlebone is unique to cuttlefish, one of the features contrasting them with their squid relatives. Cuttlebones are traditionally used by jewelers and silversmiths as moulds for casting small objects.[4] They are probably better known today as the tough material given to parakeets and other caged birds as a source of dietary calcium.

This Broadclub Cuttlefish (Sepia latimanus) can go from camouflage tans and browns (top) to yellow with dark highlights (bottom) in less than a second.

Skin

An infant cuttlefish protects itself with camouflage

Cuttlefish are sometimes referred to as the chameleon of the sea because of their remarkable ability to rapidly alter their skin color at will. Cuttlefish change color and light polarity to communicate to other cuttlefish and to camouflage themselves from predators.

This color-changing function is produced by groups of red, yellow, brown, and black pigmentedchromatophores above a layer of reflective iridophores and leucophores, with up to 200 of these specialized pigmentcells per square millimeter. The pigmented chromatophores have a sac of pigment and a large membrane that is folded when retracted. There are 6-20 small muscle cells on the sides which can contract to squash the elastic sac into a disc against the skin. Yellow chromatophores (xanthophores) are closest to the surface of the skin, red and orange are below (erythrophores), and brown or black are just above the iridophore layer (melanophores). The iridophores reflect blue and green light. Iridophores are plates of chitin or protein, which can reflect the environment around a cuttlefish. They are responsible for the metallic blues, greens, golds, and silvers often seen on cuttlefish. All of these cells can be used in combinations. For example, orange is produced by red and yellow chromatophores, while purple can be created by a red chromatophore and an iridophore. The cuttlefish can also use an iridophore and a yellow chromatophore to produce a brighter green. As well as being able to influence the color of light as it reflects off their skin, cuttlefish can also affect the light's polarization, which can be used to signal to other marine animals, many of which can also sense polarization.

Eyes

Close up of a cuttlefish eye

Cuttlefish eyes are among the most developed in the animal kingdom. The organogenesis of cephalopod eyes differs fundamentally from that of vertebrates like humans.[5] Superficial similarities between cephalopod and vertebrate eyes are thought to be examples of convergent evolution. The cuttlefish pupil is a smoothly-curving W shape. Although they cannot see color,[6] they can perceive the polarization of light, which enhances their perception of contrast. They have two spots of concentrated sensor cells on their retina (known as fovea), one to look more forward, and one to look more backwards. The lenses, instead of being reshaped as they are in humans, are pulled around by reshaping the entire eye to change focus.

Scientists have speculated that cuttlefish's eyes are fully developed before birth and start observing their surroundings while still in the egg. One team of French researchers has additionally suggested that cuttlefish prefer to hunt the prey they saw before hatching.[7]

Physiology

Circulation

The blood of a cuttlefish is an unusual shade of green-blue because it uses the copper-containing protein hemocyanin to carry oxygen instead of the red iron-containing protein hemoglobin that is found in mammals. The blood is pumped by three separate hearts, two of which pump blood to the cuttlefish's pair of gills (heart for each), and the third pumps blood around the rest of the body. Cuttlefish blood must flow more rapidly than most other animals because hemocyanin carries substantially less oxygen than hemoglobin.

Ink

Ecology

Diet

The cuttlefish uses its camouflage to hunt and sneak up on its prey. When it gets close enough, it opens its eight arms and shoots out two long feeding tentacles. On the end of each is a pad covered in suckers that grabs and pulls prey toward its beak.[8]

Range and habitat

Family Sepiidae, which contains all cuttlefish, inhabit tropical/temperate ocean waters. They are mostly shallow-water animals although they are known from depths of about 600 metres (2,000 ft).[9] They have an unusual biogeographic pattern: totally absent from the Americas, but present along the coasts of east and south Asia, western Europe, the Mediterranean, as well as all coasts of Africa and Australia. By the time the family evolved, ostensibly in the Old World, the north Atlantic possibly had become too cold and deep for these warm water species to cross.[10]

Cuttlefish is especially popular in Italy, where it is used in Risotto al Nero di Seppia (literally black cuttlefish rice). The CroatianCrni Rižot is virtually the same recipe, which probably originated in Venice and then spread across both coasts of the Adriatic. "Nero" and "Crni" mean black, the color the rice turns because of the cuttlefish ink. Spanish cuisine, especially that of the coastal regions, uses cuttlefish and squid ink for the marine flavor and smoothness it provides; it is included in dishes such as rice, pasta and fish stews.

Cultural significance

Eugenio Montale's ground-breaking debut collection of poetry Cuttlefish Bones (Ossi di seppia) was published in Turin in 1925. Montale, who grew up in Liguria along the Mediterranean Sea, was awarded the Nobel Prize for Literature in 1975, for his long and prolific career. Cuttlefish Bones remains one of the best-known and influential collections of 20th-century Italian poetry.[citation needed]

Sepia

Cuttlefish ink was formerly an important dye, called sepia. Today artificial dyes have mostly replaced natural sepia. However, recently Jewish people have resumed using sepia for the techelet dye on their Tallitstrings.[citation needed]

Contents

Anatomy

Cuttlebone

Cuttlefish have an internal structure called the cuttlebone. This is composed of calcium carbonate. It is porous, or full of small holes, in order to allow the cuttlefish the swim, not sink. Its buoyancy can change (for example, allowing the cuttlefish to go lower or higher) by changing the amount of gas and liquid in the chambers of the cuttlebone. Each species has a distinct shape, size, and pattern of ridges or texture on the cuttlebone. Cuttlebones are traditionally used by jewelers and silversmiths as molds for casting small objects. They are probably better known today as the tough material given to parakeets and other pet birds as a source of calcium for their diets. The cuttlebone is only found in cuttlefish, and is one of the features that makes them different from squid and other molluscs.

Changing color

Cuttlefish are sometimes called the chameleon of the sea because they are able to change their skin color whenever they want. Their skin can flash a colorful pattern in order to communicate with other cuttlefish and to camouflage them from predators. This color-changing function is produced by groups of red, yellow, brown, and black pigmented chromatophores above a layer of reflective iridophores and leucophores, all of these being parts of the cuttlefish's skin which help it change its color. There are up to 200 of these special pigment cells per square millimeter. The pigmented chromatophores have a sac of pigment and a large membrane that is folded when retracted. There are 6-20 small musclecells on the sides which can contract to squash the elastic sac into a disc against the skin. Yellow chromatophores (xanthophores) are closest to the surface of the skin, red and orange are below (erythrophores), and brown or black are just above the iridophore layer (melanophores). The iridophores reflect blue and green light, which make them look blue and green. Iridophores are plates of chitin or protein, which can reflect the area around a cuttlefish. They are responsible for the metallic blues, greens, golds, and silvers often seen on cuttlefish. All of these cells can be used in combinations. For example: orange would be produced by red and yellow chromatophores, while purple could be created by a red chromatophore and an iridophore. The cuttlefish could also use an iridophore and a yellow chromatophore to produce a brighter green. As well as being able to influence the color of the light that reflects off their skin, cuttlefish can also affect the light's polarization, which can be used to signal to other sea animals, many of whom can also sense polarization.

Eyes

Cuttlefish eyes are among the most developed in the animal kingdom. The organogenesis of cephalopod eyes is fundamentally different from that of vertebrates like humans.[1] Superficial, or insignificant, similarities between cephalopod and vertebrate eyes are examples of convergent evolution. The cuttlefish pupil is a smoothly-curving W shape. Although they cannot see color, they can perceive the polarization of light, which essentially enhances their ability to see contrast. They have two spots of concentrated sensor cells on their retina (known as fovea), one to look more forward, and one to look more backwards. The lenses, instead of being reshaped as they are in humans, are instead pulled around by reshaping the entire eye in order to change focus.

Blood

The blood of a cuttlefish is an unusual shade of green-blue because it uses the copper-containing protein hemocyanin to carry oxygen instead of the red iron-containing protein hemoglobin that is found in mammals. The blood is pumped by three separate hearts. Two of these are used for pumping blood to the cuttlefish's pair of gills (one heart for each gill), and the third for pumping blood around the rest of the body. A cuttlefish's heart must pump a more blood than most other animals because hemocyanin is not as good at carrying oxygen as hemoglobin is.

Ink

Cuttlefish have mouths like squid and octopuses. This ink was formerly an important dye, called sepia. Today artificial (not natural) dyes have replaced natural sepia. However, there is an increased amount of Jews in modern times using the ink for the techelet dye on their Tallit strings.

Cuttlefish as food

Cuttlefish are caught for food in Mediterranean, and East Asian cultures. Although squid is more popular as a restaurant dish all over the world, in East Asia dried cuttlefish is a highly popular snack food.

Cuttlefish is especially popular in Italy, where it is used in Risotto Nero, and in the CroatianCrni Rižot, which is almost the same and originated most probably from Venice, then spread across both coasts of the Adriatic. "Nero" and "Crni" mean black, which is the color the rice turns because of the cuttlefish ink. Spanish cuisine, especially that of the coastal regions, often uses cuttlefish and squid ink for cooking due to the marine flavor and smoothness that it provides to the meals and it is included in dishes such as rice, pasta and fish stews.

Cuttlefish in literature

Cuttlefish made their most important literary appearance in the title of Eugenio Montale's ground-breaking debut collection of poetry entitled Cuttlefish Bones (Ossi di seppia), published in Turin in 1925. Montale, who grew up in Liguria along the Mediterranean Sea, was awarded the Nobel Prize for Literature in 1975, for his long and prolific career. Cuttlefish Bones remains one of the best-known and influential collections of 20th-century poetry.

In the science-fiction novel Frek and the Elixir, by Rudy Rucker, an alien named Professor Bumby shows himself to the main character, Frek, in the form of a cuttlefish.